[BugFix]Fix precision issue for LoRA feature (#4141)

vLLM version: v0.11.0
vLLM main: vllm-project/vllm

### What this PR does / why we need it?
   Fix the precision issue of the LoRA feature in vllm-ascend.

### Does this PR introduce _any_ user-facing change?

### How was this patch tested?
```bash
pytest tests/lora/test_llama_tp.py::test_llama_lora -s
```
<img width="1319" height="879" alt="lora_test"
src="https://github.com/user-attachments/assets/2a0b2325-5b05-4bbc-ac03-a7c9f0ad9d4c"
/>


- vLLM version: v0.12.0
- vLLM main:
ad32e3e19c

---------

Signed-off-by: hukongyi <hukongyi@cmbchina.com>

vllm_ascend/lora/punica_npu.py

@@ -255,6 +255,7 @@ class PunicaWrapperNPU(PunicaWrapperBase):
         # Embedding layer only need expand op
         expand_fun: Callable = (self._expand_prefill
                                 if self.is_prefill else self._expand_decode)
+        x = x.to(torch.float32)
         expand_fun(y, x, lora_b_stacked, add_inputs)
 
     def add_lora_linear(self,